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Tsirkin" To: Guo Zhi Subject: Re: [PATCH v2 4/4] virtio_test: enable indirection feature Message-ID: <20220707015717-mutt-send-email-mst@kernel.org> References: <20220707024409.1869-1-qtxuning1999@sjtu.edu.cn> <20220707024409.1869-5-qtxuning1999@sjtu.edu.cn> <20220707005311-mutt-send-email-mst@kernel.org> <2ff418ad-0ab8-1474-4308-2d163c1e6652@sjtu.edu.cn> MIME-Version: 1.0 In-Reply-To: <2ff418ad-0ab8-1474-4308-2d163c1e6652@sjtu.edu.cn> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: eperezma@redhat.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Thu, Jul 07, 2022 at 01:56:37PM +0800, Guo Zhi wrote: > On 2022/7/7 12:59, Michael S. Tsirkin wrote: > > On Thu, Jul 07, 2022 at 10:44:09AM +0800, Guo Zhi wrote: > > > Prior implementation don't use indirection feature because there is only > > > one descriptor for every io event, actually prior implementation don't > > > support indirection because vhost can't translate and find the indirect > > > descriptors. This commit enable virtio_test malloc indirect descriptors > > > in a indirect buffer and map this buffer to vhost, thus resolve this > > > problem. > > > > > > Signed-off-by: Guo Zhi > > > --- > > > tools/virtio/virtio_test.c | 50 ++++++++++++++++++++++++++++++++------ > > > 1 file changed, 42 insertions(+), 8 deletions(-) > > > > > > diff --git a/tools/virtio/virtio_test.c b/tools/virtio/virtio_test.c > > > index 363695b33..dca408a5c 100644 > > > --- a/tools/virtio/virtio_test.c > > > +++ b/tools/virtio/virtio_test.c > > > @@ -25,7 +25,7 @@ > > > #define RINGSIZE 256 > > > #define TEST_BUF_NUM 0x100000 > > > #define BUF_SIZE 1024 > > > -/* Unused */ > > > +#define INDIRECTS_SIZE (RINGSIZE * sizeof(struct vring_desc) * 8) > > > void *__kmalloc_fake, *__kfree_ignore_start, *__kfree_ignore_end; > > > struct vq_info { > > > @@ -47,6 +47,8 @@ struct vdev_info { > > > int nvqs; > > > void *buf; > > > size_t buf_size; > > > + void *indirects; > > > + size_t indirects_size; > > What are these exactly? > The buffer is used to put indirect descriptors, and the buffer will be added > in the vhost iotlb through VHOST_SET_MEM_TABLE, so that vhost can translate > the descriptors in user mode correctly. Pls come up with a better name. indirect_buf and indirect_buf_size? And add a comment. > > > > > struct vhost_memory *mem; > > > }; > > > @@ -131,6 +133,8 @@ static void vq_info_add(struct vdev_info *dev, int num) > > > static void vdev_info_init(struct vdev_info* dev, unsigned long long features) > > > { > > > int r; > > > + int nregions = 2; > > > + > > > memset(dev, 0, sizeof *dev); > > > dev->vdev.features = features; > > > INIT_LIST_HEAD(&dev->vdev.vqs); > > > @@ -138,19 +142,25 @@ static void vdev_info_init(struct vdev_info* dev, unsigned long long features) > > > dev->buf_size = BUF_SIZE; > > > dev->buf = malloc(dev->buf_size); > > > assert(dev->buf); > > > - dev->control = open("/dev/vhost-test", O_RDWR); > > > + dev->indirects_size = INDIRECTS_SIZE; > > > + dev->indirects = malloc(dev->indirects_size); > > > + assert(dev->indirects); > > > + dev->control = open("/dev/vhost-test", O_RDWR); > > > assert(dev->control >= 0); > > > r = ioctl(dev->control, VHOST_SET_OWNER, NULL); > > > assert(r >= 0); > > > dev->mem = malloc(offsetof(struct vhost_memory, regions) + > > > - sizeof dev->mem->regions[0]); > > > + (sizeof(dev->mem->regions[0])) * nregions); > > > assert(dev->mem); > > > memset(dev->mem, 0, offsetof(struct vhost_memory, regions) + > > > - sizeof dev->mem->regions[0]); > > > - dev->mem->nregions = 1; > > > + (sizeof(dev->mem->regions[0])) * nregions); > > > + dev->mem->nregions = nregions; > > > dev->mem->regions[0].guest_phys_addr = (long)dev->buf; > > > dev->mem->regions[0].userspace_addr = (long)dev->buf; > > > dev->mem->regions[0].memory_size = dev->buf_size; > > > + dev->mem->regions[1].guest_phys_addr = (long)dev->indirects; > > > + dev->mem->regions[1].userspace_addr = (long)dev->indirects; > > > + dev->mem->regions[1].memory_size = dev->indirects_size; > > > r = ioctl(dev->control, VHOST_SET_MEM_TABLE, dev->mem); > > > assert(r >= 0); > > > } > > > @@ -170,6 +180,19 @@ static void wait_for_interrupt(struct vdev_info *dev) > > > } > > > } > > > +static int test_virtqueue_add_outbuf(struct virtqueue *vq, > > > + struct scatterlist *sg, unsigned int num, > > > + void *data, void *indirects) > > > +{ > > > + int r; > > > + > > > + __kmalloc_fake = indirects; > > > + r = virtqueue_add_outbuf(vq, sg, num, data, > > > + GFP_ATOMIC); > > > + __kmalloc_fake = NULL; > > > + return r; > > > +} > > > + > > Quite a hack. Please add comments with documentation. Also - no way to > > avoid hacks? > > The __kmalloc_fake is refered from vringh_test. > > If not using __kmalloc_fake here, the vhost doesn't know how to translate > the indirects descriptors(user address). > > We may could register a single region as large as the whole virtual space in > the vhost iotlb using 1:1 mapping. > > But since they are tests, IMHO, better here to use VHOST_SET_MEM_TABLE with > more regions. But why do we need to do this on each buffer add? > > > > > static void run_test(struct vdev_info *dev, struct vq_info *vq, > > > bool delayed, int batch, int reset_n, int bufs) > > > { > > > @@ -181,6 +204,7 @@ static void run_test(struct vdev_info *dev, struct vq_info *vq, > > > unsigned len; > > > long long spurious = 0; > > > const bool random_batch = batch == RANDOM_BATCH; > > > + void *indirects; > > > r = ioctl(dev->control, VHOST_TEST_RUN, &test); > > > assert(r >= 0); > > > @@ -188,10 +212,15 @@ static void run_test(struct vdev_info *dev, struct vq_info *vq, > > > next_reset = INT_MAX; > > > } > > > + /* Don't kfree indirects. */ > > > + __kfree_ignore_start = dev->indirects; > > > + __kfree_ignore_end = dev->indirects + dev->indirects_size; > > > + > > > for (;;) { > > > virtqueue_disable_cb(vq->vq); > > > completed_before = completed; > > > started_before = started; > > > + indirects = dev->indirects; > > > do { > > > const bool reset = completed > next_reset; > > > if (random_batch) > > > @@ -203,9 +232,13 @@ static void run_test(struct vdev_info *dev, struct vq_info *vq, > > > sg_init_table(sg, sg_size); > > > for (int i = 0; i < sg_size; ++i) > > > sg_set_buf(&sg[i], dev->buf + i, 0x1); > > > - r = virtqueue_add_outbuf(vq->vq, sg, sg_size, > > > - dev->buf + started, > > > - GFP_ATOMIC); > > > + > > > + // use indirects buffer repeatedly > > > > C style comments please. > It will be modified. > > > > > + if (indirects + sg_size * sizeof(struct vring_desc) > > > > + dev->indirects + dev->indirects_size) > > > + indirects = dev->indirects; > > > + r = test_virtqueue_add_outbuf(vq->vq, sg, sg_size, > > > + dev->buf + started, indirects); > > > if (unlikely(r != 0)) { > > > if (r == -ENOSPC && > > > started > started_before) > > > @@ -216,6 +249,7 @@ static void run_test(struct vdev_info *dev, struct vq_info *vq, > > > } > > > ++started; > > > + indirects += sg_size * sizeof(struct vring_desc); > > > } > > > if (unlikely(!virtqueue_kick(vq->vq))) { > > > r = -1; > > > -- > > > 2.17.1 > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization